CONSTITUENT QUARKS FROM QCD

Starting from the observation that colour charge is only well defined on gauge invariant states, we construct perturbatively gauge invariant , dynamical dressings for individual quarks. Explicit calculations sho w that an infra-red finite mass-shell renormalisation of the gauge inv ariant, dressed propagator is possible and, further, that operator pro duct effects, which generate a running mass, may be included in a gaug e invariant way in the propagator. We explain how these fields may be combined to form hadrons and show how the interquark potential can now be directly calculated. The onset of confinement is identified with a n obstruction to building a non-perturbative dressing. We propose seve ral methods to extract the hadronic scale from the interquark potentia l. Various extensions are discussed.